This invention relates to the preparation of high purity and highly stable polysulfides.
Organic polysulfides and particularly dialkyl polysulfides such as tetra- and penta-sulfides have been found useful for many purposes such as additives for elastomers, antioxidants for lubricating oils, intermediates for the production of organic chemicals, insecticides, germicides and as an additive to diesel fuels to improve the cetane number and ignition qualities of these fuels. These compounds have also been found useful in the compounding of extreme pressure lubricants and in the acceleration of rubber treating processes.
Methodologies are known in the art for the preparation of polysulfides by the reaction of elemental sulfur with mercaptans in the presence of a basic catalyst (European Patent 25 944) or a basic catalyst with an alcohol promotor (U.S. Pat. Nos. 3,308,166 and 3,022,351). However, problems associated with product degradation are frequently observed for polysulfide product containing 3 or greater sulfur atoms per polysulfide molecule. This degradation can cause the product appearance to change from a clear yellow or orange to a cloudy appearance and ultimately, precipitation will result. Furthermore, the presence of mercaptan and hydrogen sulfide in the polysulfide product causes a very undesirable odor which end users desire to have absent.